Controller for lifting magnets



A. E. LILLQUIST ET AL 2,390,377 CONTROLLERS FOR LIFTING MAGNETS FiledDec, 10, 1942 UNITED PATENT" OF'FECE CONTROLLER' FOR MAGNETS Arvid; E..Izillquist-,. Milwauheq; and Oliver Pr- Pnoudfoot, Wauwatosa, Wisassignor-a to Qutler-Hammer, Inc., Milwaukea, Wis, a. corporation. ofDelaware Application December 10, 19423 seriarm. 4268 520 41Glaims..(Cl. 1175-4235);

This invention relates to lifting magnet mm- In the drawing, trollersand is particularly applicable to con Figure; 1- is'a diagrammatic viewof a control trollers for use in connection with plate handling systemembodying the invention; magnets. Fig. 2 isa diagrammatic viewillustrating a Iron or steel plates of large area areordinarilymodificatiorrof the controlsystemshown in -Fig. handled by a pluralityof lifting magnets" which 1*, and

are suspended in spaced relation upon a hori- Fig: 3 illustrates amodified" form of control zontal beam associated with a traveling hoistmeans which may beused on the system shown mechanism such as an electriccrane. In installations of this type it is usually necessary to regu-Referring to Fig. 1", the same illustrates a plulate the attractiveforce of the magnets so that ralltyof lifting magnets M to M' inclusive,and plates may be lifted either singly from the top of a p li f lly p nr n t c a stock pile or ina stack and then dropped one Switches IV o 5 rrespectively cflnnecting e by one from the bottom of the stack,Heretofore operating windings of said magnets across lines the,operating windings of the several magnets 1'5 T e ag ets m y be of t y eOrdi were usually connected across a supply circuit ployed in platehandlingv in t ns, in parallel relation and in serieswith a current suchmagne usuallylectanglllar p regulating resistance and a multi point drumand being u pe in spacedrelation p a controller was provided forincluding or xamhorizontal beam associated with a traveling hoist ingsaidresistancein steps to vary the attractive ech i m. A ect CurrentVariable- Voltage force of, the magnets. In practice it has beengenerator p y d r Supplying current'to found that this type 15, magnet t1 .is open lines Li -L and in the embodiment illustrated to variousobjections. For example there is consaid gene y u r siderable, loss ofpower when the regulating re- M 0 be p wi h C re from a nsta t sistanceis included in. circuit with the magnets potential dir t c r t c in icby lines to reduce the attractive force thereof; Also. it liar-L41 hasbeen found necessary to employ a drum con.- Thefll'matule terminalsgenerator G a c troller of objectionable size in order to obtain dicatedy e ce characters T and T and variation of the attractive force of themagnets Said generator providewwith a S p r te yin relatively s u stepsandjhrough a widevrangre 3i) cited fieldwinding F which is energizedfromlines as is ordinarily required in plate. handling inthrough themedium-0f a a t b e stallationg, tentiometer rheostat 6. Motor M. isprovided The present invention has among its objgcts witha suitablecontroller 1. for-effecting starting t provide an improved Controller fplate ham and'stoppl'ng thereof andwhen started said motor dling magnetswhich overcomes the. aforemenoperates'to drivegenerator'Gat'a ConstantSpeedtioned objection5 A normally open electromagnetic switch 8 isAnother object is to provide a, variable voltage Pwvidei for connectingrminals'l and T of n- System for plate handling magnets which generatorG to lines L -L respectively. A see.

enables regulation of the. attractive force. of? the norma'ily' openelectromagnetic Switch 9 is magnets through a Wide range and inrelatively -10 provided" for connecting generatorterminal '1 small stepsby means of asmall regulating rheotonne t h edium of a resistance R statand generator terminal Tto line L throughtlie Another object is toprovide a variable voltage medium Q resistancw R switches 8 9 controlsystem of the aforesaid character for efare Se1ectw?1y controlled atmaster- Switch fecting selective energization ofthe magnets and having;an Wf position also l'ke regulation of either a single magnet or [cremeon'pos'ltmnsmarkedymfty and a plurality of magnets switches l-to Earerespectively controlled by snap Various other objects and advantages.of: the swltches "M01153 inclusw'e invention will h i ft appear Theoperation of the: aforedescribed control The accompanying drawingillustrates certain systemwmjnflwbg more mny'descfibedi embodiments ofthe invention which will now be Upon Starting motor M generatorde-scribed, it being understood that the embodiates at voltagedetermined Setting of ments illustrated are susceptible of modification.lheostat With the control m of. rheostat' 5 withoutdeparting from thespirit and scope of the in its extreme righ hand position field Windingappended claims. 55 E is connected" directly across 1inesiL .L to

I voltage.

. line L.

provide for operation ofthe generator at full Movement of the controlarm of rheostat 6 toward its extreme left hand position reduces thestrength of field winding F to thereby reduce the voltage of thegenerator.

Assuming now that generator G is operating and it is desired to liftiron or steelplates from With switches II to IE closedQcontrol switchesI l to 5 are energized from linesL L to connect the operating windingsof magnets M to M in parallel across lines L L Upon movement of I masterswitch l0 into its lift position switch 8 is energized from lines L -Lto connect lines L --L to the generator terminals T T respectively, forenergization nets M. 1

The number of plates 'Whiclrwill cling to the magnets M Whenthe sameareenergized and lifted from the stock pile is det'ermined by theattractive force of the magnets and by the weight and thickness of theplates which are being liftof the several magof generator G-at itsminimum voltage, magnets M will be subjected to substantially the fullvoltage of supply lines L L upon closure of switch 8. 'When it isdesired to reduce'the voltage of the current supplied tomagnets Mrheostat 6 is adjusted to increase the voltage of generator G and theincreased voltage of the generator bucks the voltage of supply lines L-L to thereby reduce the voltage of the current supplied to magnets'M.

' In the modification shown in Fig. 2, magnets M are supplied withreverse demagnetizing current'from lines L -L upon opening of switch 8and closure of switch 9. With switch 9 in closed position supply line Lis connected to line L through the medium of resistance R 'and supply'line L is connected to line L through the medium of resistanceRF. r V qThe generator shown in Fig. 2 may be provided with field control meansof the type shown in Fig. 3 to'enable control of the attractive force ofmagnets M by a wider range of voltage variation. As shown in Fig. 3,field winding F of the generator is connected between the adjusting ingthat a plurality of plates are lifted in a stack 7 the left to effectstep 'b step reduction of the voltage of generator G. r

- In connection ,with'the foregoing it should be noted that the voltageof generator G may be varied by means of a small size rl'. eostat toefiect variation of the attractivev force of magnets M in small stepsand, through a wide range. Also it should be noted that switches H to IEmay be operated to provide for energization of'either a single magnetora selected group of magnets and adjustment of rheostat 6 provides forlike regulation of the attractive force of either a single magnet oraplurality of magnets.

Movement of master switch In from its Lift position into its Dropposition provides for quick dropping of the load carried by the mag netsM.' Upon movement of said master switch from Lift'positi0n and its ,Dropposition switch 8 is deenergized andlswitch 9 is energized from lines LL to connect line L to generator terminal 'I through the medium ofresistance, R

and to connect line L to generator'terminal T through the medium of aresistance R 'Magnets arms of a pair of'adjustable rheostats l6 and I1,and said rheostats are connected in parallel across the supply lines L LA Wheatstone bridge circuit is thus provided for controlling thestrength and direction ofcurrent in field winding F. As is apparent, thevoltage of the generator What we claim as new and desire to secure byLetters Patent is:

1. In combination, a plurality of'lifting' magnets each having anenergizing winding, of a generator for supplying current to the windingsof said magnets, means for selectively connecting said windings inparallel relation across the output terminals of said generator, andcontrol 7 means for varying the voltage of the current supducedvalue toprovide for quick. demagnetizaof the magnets M across supply lines L L'in series with the generator G and said generator acts to buck thevoltage of said supply lines. Assuming that rheostatB is set to causeoperation plied by said generator for variation of the at-,

tractive force of said magnets, said control means including aseparately excited field winding for said generator and a rheostat forregulating the current strength of said field winding.

*2. In combination, a plurality of lifting magnets each haying anenergizin winding, a generator for supplying current to the windings ofsaid magnets, means for reversibly connecting said windings to saidgenerator and control 'means for varyin the voltag of the currentsuppliedby said generator for simultaneous variation'of the attractiveforce of said magnets. said control means, including a separatelyexcited field windingforsaid generator and a rheostat for regulating thecurrent strength in said field winding.

3. In combination. a' plurality of lifting mag nets each having anenergizing winding, a source of power, a variable voltage generatorhaving a driving motor to be energized from said source, a plurality ofelectrorespons ve switches to be energized from said source forselectively connecting said windings in parallelrelation, a pair ofelectroresponsive control switches to be energized from said sourcealternatively, one of said last mentioned switches being responsive tosupply current from said generator to said magnet windings in onedirection and the other beingrespon- The attracsive to supply current tosaid windings in a reverse direction, and control means for varying theVoltage of the current supplied by said generator for variation of theattractive force of said magnets, said control means including a fieldwinding for said generator to be supplied with current from said source,and a rheostat for regulating the current strength of said field windng.

4. In combination, a plurality of lifting magnets each having anenergizing winding, a source of power, a variable voltage generatorhaving a driving motor to be energized from said source, means forconnecting said windings in parallel relation, a pair ofelectroresponsive control switches to be energized from said sourcealternatively, one of said control switches being responsive to supplycurrent from said generator to said magnet windings in one direction andthe other being responsive to supply current to said windings in areverse direction, resistance means to be included in circuit with saidmagnet windings upon response of said last mentioned switch and controlmeans for varying the voltage of the current supplied by said generatorfor variation of the attractive force of said magnets, said controlmeans including a field winding for said generator to be supplied withcurrent from said source and a rheostat for regulating the currentstrength of said field winding.

ARVID E. LILLQUIST. OLIVER P. PROUDFOOT.

